1. Field of the Invention
This invention relates to an extemporaneous injector assembly for use in transfusions and perfusions. More particularly, this invention relates to an injector which can be used in combination with a feeding means (e.g. a syringe) for feeding, into a transfusional or perfusional liquid, a nourishing solution, a vitamin solution, a medicinal solution, an anticoagulant solution or a like solution, wherein penetration of a hollow piercing member (e.g. a syringe needle) into the injector body is not necessary.
2. Description of the Prior Art
It is well known that during transfusions and perfusions, the periodic addition of various substances to the transfusional or perfusional liquid may be desirable or necessary. For instance, in blood transfusions, the addition of an anticoagulant such as heparin is the customary practice. When transfusional reactions occur, the addition of antipyretic agents may be necessary. The commonest of such transfusional reactions is the reaction induced by pyrogens contained in the transfusion liquid or in the devices used for transfusional purposes. The pyrogens are fever-producing substances, i.e. substances capable of inducing in a patient a marked temperature rise accompanied by shivering. As a further instance, there can be mentioned the periodic addition of nourishing solutions containing vitamins to the transfusional liquid fed through the epicranial vein to prematurely born babies.
To carry out such periodic or intermittent additions, devices known as "extemporary (or intermittent) injectors" have heretofore been in general use. These known injectors essentially comprise a tubular portion which is fitted in series in the tubular conduit conveying the perfusional or transfusional liquid to the patient.
The injectors at present in general use are made from elastomeric materials because the connection between the injector and the source of the solution which is intermittently or occasionally to be injected into the perfusional or transfusional liquid is achieved by forced penetration of a hollow piercing member through the injector wall. Usually, a syringe containing the solution to be injected is employed. The needle of the syringe is used to puncture the injector wall and thus to penetrate into the injector body. When the needle is withdrawn upon termination of the addition, the hole formed by the needle closes in view of the elastic nature of the wall, thus ensuring that the injector is sealed. This sealing is possible since the pressure exerted by the circulating liquid on the wall of the tubular conduit is relatively low.
However, the simplicity of the extemporary injectors in use at present results in disadvantages which are attributable to the extremely unsophisticated structure of the injectors.
These disadvantages are essentially due to the fact that every addition of solution, even during the same use of a single injector, requires a new hole to be made in the injector wall. Since, for the sake of economy, the same injector should be used for several perfusions or transfusions, it is apparent that in the long run the injector structure weakens, and that, after many punctures, the injector wall is no longer adequately sealed. It can in fact easily experienced that it is not necessary to repeatedly puncture always the same point of the injector wall to compromise the sealing of a certain zone of the injector. This disadvantage is particularly serious because a lack of sealing might occur suddenly in the course of use when withdrawing the needle after many punctures. In such a case, should the lack of sealing be extensive, the transfusion ought to be discontinued at once.
A further disadvantage of the extemporaneous injectors at present in use is the necessity to use a needle for hypodermic or intravenous injections. The cost of the needles weighs heavily on the general costs of the transfusion unit, particularly in view of the ever increasing frequency of the injections into the perfusional or transfusional liquids.